Inertial wave dynamics in a rotating liquid metal

The dynamics of free and forced inertial waves inside cylinders of different aspect ratios A = H0/2R0 are studied experimentally. The liquid metal GaInSn was choosen as fluid in order to enable a contactless stimulation of the flow inside the cylinder by means of AC electromagnetic fields. The ultrasound Doppler velocimetry was used to record the flow structure and the inertial waves. Our experiments demonstrate the capability for selective excitation of different inertial wave modes by deliberate variations of the magnetic field parameters. The application of time-modulated AC fields turned out to be an efficient method for triggering inertial waves. Furthermore, it was found that turbulent fluctuations in a swirling flow driven by a rotating magnetic field are able to provoke one specific inertial wave mode inside the cylinder and that such an inertial wave is able to survive over a distinct time. Experiments at the fundamental resonance have shown that multiple harmonic oscillation modes appeared simultaneously. The measured inertial wave frequencies were compared to the predictions of the linear inviscid theory.